Project Summary Multidrug resistant (MDR) bacterial infections are expected to claim 10 million lives by the year 2050. To combat the rise in MDR bacterial infections, it is crucial that we develop novel classes of antibacterial agents. While progress has been made towards the development of novel classes of antibiotics against Gram-positive bacteria within the past decade, a novel agent for Gram-negative bacteria has not been introduced since 1968. The lack of success regarding the development of Gram- negative bacterial agents is largely attributed to the complex composition of their outer membrane and its impermeability to most small molecules. Moreover, the poor understanding of the physicochemical features that influence accumulation in Gram-negative bacteria underlies the lack of progress in this field. To overcome this obstacle, recent work in our laboratory led to the identification of guidelines for accumulation in E. coli that included the presence of an unencumbered ionizable amine, low flexibility (RB ? 5), low 3-dimensionality (Glob ? 0.25). In Specific Aim 1, rules for compound accumulation will be applied in the transformation of Ribocil C, a synthetic compound with promising activity against Gram- positive bacteria, into an antibacterial agent with a broadened spectrum of activity. In Specific Aim 2, lead compounds will be evaluated for their translational potential in in vivo studies of toxicity and efficacy. The results from these studies will provide strategies for expanding the chemical diversity of Gram-negative antibiotics, and further define a general blueprint for the conversion of Gram-positive- only compounds into broad-spectrum antibiotics in order to combat emerging resistance. The training environment at UIUC features state-of-the-art facilities and offers many collaborative opportunities with world renowned scientists. The resources and collaborations at this university will aid in accomplishing many of the proposed experiments and designs. The Hergenrother group is also extremely well versed in the fields of chemical synthesis, chemical biology and molecular biology. Any gaps in my research experience and knowledge can be filled through interactions with fellow postdocs and graduate students or through the courses I will be attending during my stay. Overall, the environment in this lab will facilitate the research proposed in the research strategy.